Phosphonate corrosion inhibitors are recognized for their effectiveness in protecting metals from corrosion, particularly in various aggressive media. They act by forming a protective layer on the metal surface, which can be attributed to their ability to adsorb onto the metal surface through chemical bonds or physical forces 。
Experimental methods such as weight loss measurements, polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) are commonly utilized to evaluate the inhibition activity of these phosphonate derivatives 。The results from these methods have demonstrated that phosphonates can significantly reduce the corrosion rate of metals like carbon steel, especially when used in combination with other inhibitors such as zinc ions 。
Theoretical approaches, including Density Functional Theory (DFT) and Molecular Dynamic Simulations (MDS), have also been employed to gain insights into the structural and electronic properties of phosphonate inhibitors and their interaction with metal surfaces 。DFT calculations can correlate the experimental inhibition efficiencies with quantum descriptors of the inhibitive molecules, such as the energy of the Highest Occupied Molecular Orbital (E_HOMO) and the Lowest Unoccupied Molecular Orbital (E_LUMO), while MDS can determine the adsorption modes and calculate the adsorption energies of the inhibitors on the metal surface 。
It has been found that the presence of phosphonate or phosphonic acid functional groups in the molecular structure of these inhibitors is directly linked to their high inhibitory activity 。Moreover, the adsorption energy of phosphonates and phosphonic acids on metal surfaces increases with the increase in the number of phosphonate groups in the molecule, indicating a stronger protective effect with more phosphonate groups 。
In summary, phosphonate corrosion inhibitors offer a promising avenue for metal corrosion protection, with both experimental and theoretical studies confirming their effectiveness and providing insights into their mode of action 。